An Innovative ELS System on Recently Reclaimed Land – Construction and Performance

On the recently reclaimed land for the airport three-runway system, deep excavations have been carried out to construct tunnels connecting the terminals. A novel excavation and lateral support (ELS) design comprising a double wall system connected by ties was introduced in one portion to cater for the challenging geotechnical condition with improved constructability at the site adjacent to the shoreline. This paper will briefly discuss the development of the scheme, then focus on the construction and performance of the system. The design was developed through close collaboration between the designers and contractor, based on a thorough site investigation and analyses. It offered a cost-effective construction option allowing clear access to the cofferdam, flexibility for lifting and logistics, and efficient structure construction processes. The robustness of the system could also be enhanced by additional ground improvements across a limited extent. The performance of the system during construction has been reviewed by comparing the predicted deflection of the temporary vertical walls in design analyses with the monitoring data. It is observed with positive results giving confidence in the implementation of deep excavation with a double wall system. Site observations are also shared with recommendations of potential improvements for future implementation.